Project Summary/Abstract The inability to produce sustainable health behavior changes is a major barrier to reducing the burden of chronic disease. Tremendous research efforts to promote health protective behaviors and reduce health risk behaviors have been undertaken for decades, but are not reflected in the low prevalence of healthy lifestyles observed in the United States. This competitive revision responds to the call for a more systematic, mechanisms-focused approach to behavior change research advocated in RFA-RM-17-022. The rationale for this proposed research is that physical activity (PA) is a critical factor in sustained weight loss, and influences chronic disease both directly, and through its effects on weight management. However, most individuals are not able to achieve and/or sustain the levels of PA recommended for weight management or decreased disease risk. Improvements are needed to current behavior change approaches in order to increase PA in the population. The overall objective of this competitive revision is to evaluate executive functions (EF) and centered identity (CI) as potential targets for increasing PA. EF has been identified as a potential target for behavior change by the Science of Behavior Change (SOBC) Network and will be evaluated using assays included in the SOBC repository. Many existing approaches rely heavily or exclusively on the successful recruitment of EF to self-regulate behavior. However, because EF is effortful and prone to error, it should be reduced over time and supported by other approaches in order to maintain behavior changes. This widely recognized shortcoming of EF inspired a new model of behavior change, The Maintain IT Model of Health Behavior Change and Maintenance (Maintain IT). The Maintain IT model proposes that facilitating shifts in centered identity (CI, a self-representation that is consistent, rather than at odds with the behavior, and is more resilient in the face of stress and setbacks) can reduce the burden on EF for successful self-regulation. The study design of this competitive revision involves adding measures of EF and CI to an ongoing NIH-funded clinical trial (R01 DK111622) designed to compare 1 year weight loss induced by intermittent fasting versus daily caloric restriction. Importantly, all subjects in the parent trial receive a 1 year behavioral weight loss program which includes a guidelines-based prescription to increase moderate intensity PA to 300 min/week. The specific aim is to evaluate the role of EF and CI in predicting initiation and maintenance of PA in individuals with obesity enrolled in a behavioral weight loss intervention. The central hypothesis is that EF and CI will jointly predict objectively-measured short-term and long-term PA adherence, with CI explaining increasing amounts of the variance over the longer term. The study is significant as if either EF or CI are identified as important mechanisms for health behavior change, future work can focus on creating interventions to effectively target EF and CI to improve our ability to facilitate sustainable health behavior change.